1. Field of the Invention
The present invention relates to a communication system and a handshake method thereof. More specifically, the present invention relates to a communication system and a handshake method thereof for use in a wireless network.
2. Descriptions of the Related Art
The IEEE 802.16 is a major technology for broadband wireless access. Relay technology is used to extend the coverage and solve the dead spot problem. Currently, the relay technology in the IEEE 802.16 is defined in the IEEE 802.16j standard. Although the IEEE 802.16j standard already provides the solution for the dead spot, there still exist some defects of service path (e.g. FTP, e-mail, and so on) addition. A hashed message authentication code/cipher-based message authentication code (HMAC/CMAC) tuple is used to protect a control message not to be stolen and/or altered in IEEE 802.16j standard. For example, if a base station (BS) intends to transmit a control signal with an HMAC/CMAC tuple to a mobile station (MS), the HMAC/CMAC must comprise an MS authentication code for the MS to authenticate whether the control message is stolen and/or altered according to the HMAC/CMAC tuple.
Since the HMAC/CMAC tuple only comprises the MS authentication code, a relay station (RS) along the same relay path with the MS can only read the information of the control message but not to authenticate completeness of the control message. If the RS wants to authenticate the information of the control signal, the BS must transmit control signal with HMAC/CMAC comprising an RS authentication code to the RS. That means that the BS must transmit the control message with the same information twice (i.e. to the RS and to the MS), which increases the extra load in the relay path. Transmitting a control signal in the opposite direction, i.e. from the MS to the BS, also faces the same problem.
Consequently, how to make the BS/MS transmit the control signal with the HMAC/CMAC tuple only once and make all RSs and BSs along the same relay path can receive the control signal and authenticate completeness of the control message is still an objective for the industry to endeavor.